Magnetic core



hema sept `19, 195o MAGNETIC com:

Gareth G. Somerville, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York Application January 1s, 1941, serial No. 122,837

l a new and improved method of making a magnetic core.

A further object of the invention is to provide a new and improved unitary magnetic core for three phase induction apparatus.

A still further object of the invention is to provide a new and improved method of making a three phase magnetic core.

The invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claim.

In the drawings, Fig. 1 is a perspective view of an embodiment of the invention; Fig. 2 is a detailed exploded view which illustrates the joints between the leg and yoke portions of the core; Fig. 3 is a modification which illustrates a lower loss type joint between the leg and yoke portions of the core, and Fig. 4 is another modification for accomplishing a purpose similar to that of Fig. 3.

Referring now to the drawings and more particularly to Fig. 1, the core is shown as comprising three straight laminated leg portions l, 2 and 3. These legs are parallel to each other and their relationship in space may be described by likening them to elements of a right circular cylinder which are equally or symmetrically spaced with respect to each other. The ends of the legs I, 2 and 3 are joined by closed loop laminated yoke members l and 5. The laminations of al1 the members are preferably made from grain oriented magnetic strip material having a highly favorable magnetic direction along their length. One such material is high reduction, cold rolled silicon strip steel.

The three legs which are all the same and whose laminations may all be the same width and length are made by lengthwise staggering or oifsetting alternate laminations or groups of laminations. As shown most clearly in Fig. 2, alternate laminations are on'set so that when considered from left to right, the odd numbered laminations extend lengthwise beyond the even numbered laminations. At the other end, the reverse will be true and the odd numbered laminations will be the short ones relative to the even numbered lamlnations. However, as indicated above, it is not essential that the alternate laminations be staggered. For example, the staggering may be made to occur in groups of 2, 3, 4 or any suitable number of laminations.

The yokes are preferably made according to the teachings of my prior applications, Serial No. 536,749, filed May 22, 1944, now Patent No. 2,456,458, granted December 14, 1948, and assigned to the present assignee. Briefly, the method comprises cutting the pieces from a long strip of magnetic material in progressively changing lengths and assembling them in a jig in such a way that there are three pieces per layer with the ends of the pieces in each layer making abutting contact andy with the abutting contacts of the ends of the pieces in adjacent layers or groups of layers being staggered. By applying pressure to the assembled laminations, the yoke portions 4 and 5 may be formed in the shape shown. Prior to the assembling of the core, the

core and yoke portions are strain relief annealed and it will be observed that with the parts illustrated in the drawing, very good space factor in the annealing oven is obtained because the legs 6 are straight and can be packed very completely in the oven. Similarly, the yokes I and 5 will also occupy relatively small space and will have a substantially smaller diameter than in the finished core because the ends of the three parts making up each yoke will be tted together instead of being expanded so as to join the legs as in the finished core.

After the annealing operation, the three equally curved laminated parts which form each yoke and which join each other with butt and lap joints are separated by pulling them apart, as

shown most clearly in Fig. 2, and their staggered ends are interleaved with the staggered ends of the leg portions of the core so as to form lap joints as shown at the top of Fig. 1. In performing this latter operation, it will be found that a part of the outer layer of the yokes can be discarded so that, as shown in Fig. 2, the outer layer of the yoke will have two short portions which abut against the sides of the outer layer of the leg whereas the second outermost layer of the yoke will have two long laminations which iit in between the first and third laminations of the leg. These make butt contact at the bottom with the second lamination layer of the leg and make butt contact with each other at their ends, as shown in Fig. 1.

It has been found that the width of the yoke portions need only be about one-half the width of the leg portions for substantially uniform flux 3 dmtyinthevarisparhdihece nxisis becanaeotheveetrehtimdthelegandyoke iiuwhiehresulisinthehtalnlueottheyoke flux being substantially le. han the value of theuxinitsle- Inthemodicattmahu'nlnntheyoke ismdesomewhatdiilerentbmastoreducethe asinllig.1.

what I claim as new and desire to secure by DettenPatentoitheUnitedBtath:

A three phase magnetic core comprising. in combination. two similar hexagonaliy shaped yoke coaxially spaced from each other, each yoke comprising three similar laminated memberseachhavingastraightcentralpartbetween integral straight end portiom which make equal angle with the central part, the laminations of the yoke members being radially nested and having alternatingly extending end portions. and three straight parallel laminated leg members. the laminations ot the leg members being ilat and being arrangui to iorm alternstingly extending end portions, the end portions of each leg being interleaved respectively with the end parts of two yoke members. the number of leg laminations being equal to the number oi yoke laminations, the width of the leg laminations being substantially twice the width of the yoke iaminations.

GAREI'H G. SOMERVILLE,

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATE PATENTS Number Name Date 644,565 Arnold Mar. 6. 1900 999,825 McConahey Aug. 8, 1911 1,280,806 Moody Oct. 8. '1916 1,365,569 Troy Jan. 11, 1921 2,394,648 Woolloik Feb. 12, 1946 FOREIGN PATENTS Number Country Date 8,152 Great Britain May 2, 1900 OTHERREFERENCBB Die Wechselstrom Technik (Die Transformatoren) by E. Arnold Und J. L. La Cour Zweiter Band 2 Auflage Berlin, 1910, pages 89 to 92. 

